Boosted engines are in common use in which air is compressed by an air compressor powered by either a turbo positioned in the engine exhaust or powered by the engine crankshaft. Compression will increase air temperature. Consequently the compressed air is often routed through a heat exchanger commonly referred to as a charge air cooler before entering the engine air intake system. Under high ambient air humidity conditions condensate will form in the heat exchanger. In some prior approaches condensate is always routed into the engine exhaust and in other prior approaches condensate is always routed into the engine air intake.
The inventors herein have recognized that always routing the condensate to either the exhaust or the air intake regardless of engine operating conditions and regardless of whether there are contaminants in the condensate has led to undesirable engine or catalyst operation. For example, always routing condensate to the air intake system may result in rough engine operation under some operating conditions. And always routing condensate to the exhaust upstream of a catalyst at low or moderate engine loads may result in undesired catalyst cooling. Further, if engine oil is present in the condensate routing the condensate to the catalyst may result in undesired catalyst operation. Further, throwing away the engine oil by dumping it into the engine exhaust downstream of the catalyst is undesirable from an emissions or efficiency perspective.
The inventors herein have solved these issues by a method, in one example, which comprises: routing air from a compressor through a heat exchanger to a combustion chamber of the engine; coupling condensate formed in the heat exchanger through a passage coupled to the combustion chamber; accumulating a portion of the compressed air in an accumulator; and when the engine output is below a predetermined amount, coupling a part of the accumulated air through the passage into the combustion chamber. If the accumulated air is not used, the condensate would tend to accumulate on surfaces and poor engine operation may result. At higher loads there should be sufficient air velocity to prevent such accumulation so the accumulated air may not be needed at high loads.
In another example, when oil is not detected in the condensate it may be routed to the engine exhaust upstream of the catalyst to cool the catalyst. When oil is present in the condensate, it is directed to the engine for combustion. And, at low engine loads, accumulated air also is introduced with the condensate.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.